The disinfection method that leaves no residual effect in water is: MCQ with Answer and Explanation

The disinfection method that leaves no residual effect in water is:
A. Ozonation
B. Chlorination
C. Chloramine treatment
D. Bleaching powder
Answer: Option A
Solution (By JKSSB Mock Tests)
Ozone decomposes quickly to O₂, leaving no residual disinfectant. Thus a small chlorine dose may be added after ozonation for distribution protection. Chlorine provides residual protection.

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Practice More chemistry Questions

Question #1
Which of the following metals is stored under kerosene?
A. Sodium
B. Zinc
C. Iron
D. Copper

Correct Answer: Option A


Explanation:
Sodium reacts vigorously with moisture and oxygen in air, so it is stored under kerosene to prevent contact. Potassium, lithium are similarly stored. Iron, zinc, copper do not require such storage.

This question belongs to: Science chemistry
Question #2
A gas at 2 atm pressure occupies 5 L. What is its volume if pressure is increased to 5 atm at constant temperature?
A. 2 L
B. 1 L
C. 10 L
D. 12.5 L

Correct Answer: Option A


Explanation:
Boyle's law: P₁V₁ = P₂V₂ → V₂ = P₁V₁/P₂ = (2 atm × 5 L)/5 atm = 2 L. Pressure increased, so volume decreases.

This question belongs to: Science chemistry
Question #3
The force that holds atoms together in a molecule is called:
A. Magnetic force
B. Nuclear force
C. Chemical bond
D. Gravitational force

Correct Answer: Option C


Explanation:
Chemical bonds are attractive forces between atoms due to electron interaction—ionic (transfer), covalent (sharing), metallic, etc. These bonds hold atoms together in molecules or crystals. Nuclear force holds protons and neutrons in nucleus. Gravitational and magnetic forces are negligible at atomic scale. Bond energy determines stability; stronger bond means more energy required to break.

This question belongs to: Science chemistry